1. Field of the Invention
The invention relates to a modification of a light-emitting device.
2. Related Art
Conventionally, a LED chip mounted on a substrate is sealed with glass, thereby forming a LED lamp. WO2004-982036 discloses a method of forming plural LED lamps in which plural LED lamps arranged in a lattice pattern on a plate-like ceramic substrate are collectively sealed with glass and dried. In addition, JP-A 2006-344450 discloses a linear light source formed by linearly arranging plural LED chips on a linear substrate and collectively sealing with glass.
In accordance with use of LED lamp in various light emitting situations, flexibility of light extracting direction and heat dissipation for high brightness are required to be improved in the LED lamp. WO2004-982036 and JP-A 2006-344450 are not configured to actively extract light in a lower surface direction of a substrate on which a LED element is mounted, and the flexibility of light extracting direction is poor. In addition, since the heat dissipation structure is not provided, the heat dissipation is not improved.
In the meantime, a linear expansion coefficient of the substrate for mounting on the LED element is different from that of a glass material for sealing the LED element. As a result, when the glass material is bonded by thermal compression and cooled during a sealing process, a difference is generated between the amount of shrinkage of the substrate and that of the glass material. The difference in the amount of shrinkage becomes significant with increasing a bonded surface of the substrate to the glass material for sealing. In the configuration of WO2004-982036 and JP-A 2006-344450, since the plural LED chips are correctively sealed with glass, the difference in the amount of shrinkage between the substrate and the glass material for sealing becomes significant, and a crack is generated in the sealing glass after cooling. This causes a decrease in yield.
Therefore, one object of the invention is to improve flexibility of light extracting direction of a light-emitting device. In addition, another object is to improved heat dissipation of the light-emitting device. Further another object is to provide a light-emitting device in which a crack is not generated in the sealing material.